Regarding the medicine issue, I take the following view of priestly healing.
When a person studies the religious literature of their god, to a differing
degree there is medical advice. Some of these have rapid effects, others
are slow and less dramatic. Some are limited to in the number of uses
(spells, which must be restored), others can be applied without proscribed
limits (proficiencies). Both have their source in the wisdom literature of
the various religions. One could view the differences as fundamental (one
is magic, one is mundane), but I do not. IMC, these differences are a
difference in degree. All of it has to be learned and understood (INT
governs how many prof slots a charcter has, application of Healing is a
WIS-2 check).
What is the difference?
1) time spent understanding the powers inherent in materials, words,
gestures, the life force, the divine nature of things, disciple, &c.
2) access to ever more secret books, teachings, and techniques. Secret
teachings are a part of every religion.

Ultimatly, only one who undergoes training as a priest can cast spells, but
the training required to learn the basics of healing can be learned outside
the priest class (3 slots, though).

Kenneth Gauck